The invention is particularly useful for the treatment of shoulder dysfunction. An estimated 555,000 persons are disabled each year in the United States of America by cerebrovascular accidents (CVA) such as stroke. Many of these patients are left with partial or complete paralysis of an extremity including for example, hemiplegic subluxation (incomplete dislocation) of the shoulder joint. This is a common occurrence and has been associated with chronic and debilitating pain among stroke survivors. In stroke survivors experiencing shoulder pain, motor recovery is frequently poor and rehabilitation is impaired. Thus, the patient may not achieve his/her maximum functional potential and independence. Therefore, prevention and treatment of subluxation in stroke patients is a priority.
There is a general acknowledgment by healthcare professionals of the need for improvement in the prevention and treatment of shoulder subluxation. Conventional intervention includes the use of orthotic devices; such as slings and supports, to immobilize the joint in an attempt to maintain normal anatomic alignment. The effectiveness of these orthotic devices varies with the individual. Also, many authorities consider the use of slings and arm supports to be controversial or even contraindicated because of the potential complications from immobilization including disuse atrophy and further disabling contractures.
Surface, (i.e., transcutaneous) electrical muscular stimulation has been used therapeutically for the treatment of shoulder subluxation and associated pain, as well as for other therapeutic uses. Therapeutic transcutaneous stimulation has not been widely accepted in general because of stimulation-induced pain and discomfort, poor muscles selectivity, and difficulty in daily management of electrodes, which necessitates a highly specialized clinician for treatment. In addition to these electrode-related problems, commercially available stimulators are relatively bulky, have high-energy consumption, and use cumbersome connecting wires.
In light of the foregoing deficiencies, transcutaneous stimulation systems are typically limited to two stimulation output channels. The electrodes mounted on the surface of the patient's skin are not able to select muscles to be stimulated with sufficient particularity and are not suitable for stimulation of the deeper muscle tissue of the patient as required for effective therapy. Any attempt to use greater than two surface electrodes on a particular region of a patient's body is likely to result in suboptimal stimulation due to poor muscle selection. Further, transcutaneous muscle stimulation via surface electrodes commonly induces pain and discomfort.
Studies suggest that conventional interventions are not effective in preventing or reducing long term pain or disability. Therefore, it has been deemed desirable to develop a therapy for the treatment of shoulder dysfunction which involves the use of a percutaneous, (i.e., through the skin,) neuromuscular stimulation system having implanted, intramuscular stimulation electrodes connected by percutaneous electrodes leads to an external and portable pulse generator.